AR-15 Fliers, Part 2

Ammunition-related causes of fliers.

by Joe Carlos

Last month we said that two of the most common causes of fliers are gas tube misalignment and ammunition issues. We’ll begin by jumping into imperfections in cartridge concentricity which is a major cause of fliers in any rifle or pistol. Our goal is to send bullets straight into the back of the barrel. If cartridge concentricity is compromised, bullets are set at a slight angle in the neck. When fired, they will enter the back of the barrel at an angle and deform.

It is possible to measure the runout using a gauge like the Hornady Concentricity Gauge (Hornady #050076). Runout is present in both factory and handloaded cartridges. Rifles vary in their tolerance to runout. Generally, guns jumping bullets further, either because they were chambered with long freebores or have eroded throats due to high round counts, will exhibit the lowest tolerance to runout. As a general rule, I don’t like to see competitors using ammo that has anything over 0.003” of runout. The Hornady tool will also allow the user to actually straighten bullet alignment. Gauging ammunition, rounds with high runout that are straightened should be separated and tested to note any differences from those that started straight.

I am abbreviating this topic of concentricity by including some target scans that speak for themselves. A more thorough discussion is in my April 2016 and December 2018 articles. Pay attention to how the…

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